This invention relates to a method in which members moving repeatedly or those receiving them used in machinary are reinforced with some hard material. According to the conventional method of this kind for reinforcing, members to be reinforced and the reinforcing hard material are not unified materially but are connected mechanically by such means as screwing, caulking and riveting. Thus, the attached hard material becomes loose while the reinforced member is subject to repeated impacts. Further, because the reinforcing hard material requires a size necessary not only for reinforcement but also for being attached, it has to be of a size unnecessarily large for reinforcement and it is difficult to reinforce small portions or workpieces very locally. The reinforcing work with mechanical attachment of hard material takes long time and is troublesome because of preliminary steps such as machining and boring. When the member to be reinforced is a mechanically weak one such as laminated silicon steel plates used as a plunger in an electromagnet, the reinforcement by mechanical attachment of hard material is limited in its reinforcing effect and in its range of application.
Then, the object of the present invention lies in providing a reinforcing method making use of friction welding in which reinforcement can be applicable very locally and reinforcing work is simple and efficient.